Minimum oil interrupter in dead tank bulk oil power circuit breaker construction

ABSTRACT

A minimum volume oil interrupter is immersed in the oil of a dead tank bulk oil circuit breaker and is operated by the conventional operating mechanism of the bulk oil breaker. The minimum volume interrupter vents to the external atmosphere through a hollow tube in the terminal bushing.

[45] Aug. 20, 1974 United States Patent Guaglione References Cited UNITED STATES PATENTS MINIMUM OIL INTERRUPTER IN DEAD TANK BULK OIL POWER CIRCUIT BREAKER CONSTRUCTION ,815 4/1961 Leeds et ZOO/I48 B Giovanni Paolo Guaglione, La

[75] Inventor:

Primary Examiner-Robert S. Macon Attorney, Agent, or Firm0strolenk, Faber, Gerb & Soffen 22 Filed:

[57] ABSTRACT A minimum volume oil interrupter is immersed in the Dec. 26, 1972 21 Appl. No: 318,497

oil of a dead tank bulk oil circuit breaker and is operated by the conventional operating mechanism of the 51 I l zoo/150 zoo/150 ZOO/150 H bulk oil breaker. The minimum volume interrupter 1 nt- C H......................... vents to the external atmosphere through a ho low tube in the terminal bushing.

[52] US. Cl.......

H0lh 33/68 ZOO/148 B, 148 G, 150v B,

[58] Field of Search 200/150 D, 150 E, 150 G, 150 R, 15OH 7 Claims, 2 Drawing Figures PAIENIEU 10:20am

SHEET 1H 2 MINIMUM OIL INTERRUPTER IN DEAD TANK BULK OIL POWER CIRCUIT BREAKER CONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to high voltage power circuit breakers, and more specifically relates to the use of low oil volume interrupters in a dead tank, bulk oil circuit breaker.

In a conventional dead tank, bulk oil circuit breaker, an elongated contact passes through an interrupter chamber and its upper end engages a stationary contact at the top of the chamber. The interrupter chamber is totally immersed in oil which is carried in a grounded tank. The lower end of the elongated contact is moved between an engaged and disengaged position within the .interrupter chamber by means of an external conductive crossbar which also serves to connect the interrupter in series with another interrupter within the tank.' Upon interruption, the conductive crossbar moves down, and the top of the movable, elongated or bayonet contact leaves the stationary contact within the interrupter and an arc .is drawn; between the sepa-' rating contacts. The arc extinguishing process causes the creation of hot exhaust gases which vent through ports in the interrupter .chamberandsinto the large bulk of oil within the grounded tank. Moreover, the rapidly expanding gas bubble displaces large quantities of oil, resulting in substantial reaction forces, causing strain on many breaker parts such as the tank, the bushings which support the interrupters, the tank head, andthe like. These reaction forces also cause substantial foundation loading. Breakers of this general type are shown in US. Pat. No. 3,335,245, entitled COMBINED TANK LINER INTERPI-IASE BARRIER FOR OIL CIRCUIT BREAKERS (PC-92).

The present invention seeks to relieve the substantial reaction forces which-must be supported in the conventional dead tank oil circuit breaker.

Another general type of high voltage circuit interrupter is known as a minimum oil interrupter. These devices are'conventionally mounted in a live tank housing where the housing is at high potential above ground at the top of a porcelain column. Minimum oil interrupters have arc extinguishing chambers which confine a small volume of oil. High pressure is generated by expanding gases created from this oil due to arcing in the interrupting chamber. This gas pressure is relieved by allowing the gas to vent axially and across the arc and to external regions. These interrupters do not encounter high forces perpendicular to the axis of the interrupter due to this jet reaction force which accompanies the operation of the bulk oil immersed interrupter described previously. Moreover, the gases produced in-a minimum volume interrupter reach the main bulk of oil of the device at a greatly reduced expansion rate. The mounting of these interrupters at the top of an insulation column has the disadvantage of difficult maintenance, high oil maintenance, vulnerability to wind, ice and earthquakes, and the lack of an isolating break.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to the novel use of a minimum oil circuit interrupter in a dead tank bulk oil circuit breaker with exhaust gases being exhausted through a channel in the terminal bushing of the assembly. Thus,

a conventional minimum oil interrupter having are extinguishing chambers, resulting in very high pressures within the chamber is adapted to the bottom end of a bushing of a dead tank bulk oil circuit breaker. The moving contact is spring-loaded within the arcing chamber and protrudes through an oil and gas-tight seal at the bottom end of the interrupter, into the oil of the main breaker tank. A contact is affixed to the bottom end of the moving contact rod and is engageable with disconnect contacts carried by the conventional conductive crossbar. Thus, during the closing stroke of the movable crossbar, the crossbar contact engages the movable contact rod bottom end and drives the rod upward to engage the interrupter stationary contact. During this closing stroke, a set of opening springs in the bottom of the interrupter are compressed;

During the opening stroke, these charged springs help to accelerate the movable contact rod and crossbar downwardly toward a contact disengaged position. As the interrupter contacts open, they draw an are which causes the small volume of oil in the chamber. to at least partly disassociate to produce a gas under high pressure. This gas then vents through the arc and through a channel in the circuit breaker bushing to relieve the pressure within the arcing chamber. Alternatively, the gas can be vented by a suitable insulated BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates, in partial cross-sectional view, a bulk oil, dead tank circuit breaker having minimum volume oil interrupters mounted therein in accordance with the invention.

FIG. 2 is an enlarged cross-sectional diagram of the minimum volume interrupter used in the assembly of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, there is shown a conventional bulk oil, dead tank circuit breaker which consists of an outer metallic tank housing which is at ground potential and which is filled with oil to the level 11. Two bushings l2 and 13 enter the tank top in conventionalfashion. These bushings are modified, however, in that there are hollow central conduits l4 and 15, which could be the bushing conductors extending through the center of the bushings to regions external of the breaker tank.

A conventional operating mechanism 16 enters the tank and is connected to the conductive crosshead l7. Crosshead 17 has two movable disconnect contacts 18 and 19 thereon which are connectedto one another and which cooperate with interrupters 20 and 21 re spectively. Interrupters 20 and 21 are supported from bushings l2 and 13 as shown. Crosshead 17 is shown in the breaker-closed position in solid lines and in the breaker-open position in the lower dot-dash lines.

In accordance with the invention, interrupters 20 and 21 are of the minimum oil type and have upper head castings connected to the ends of bushings 12 and 13 in any desired manner. These connections are covered by conventional corona shields 22 and 23 respectively. The construction of the interrupters and 21 may be of any conventional minimum oil .interrupter type and typical interrupter 20 is shown enlarged in FIG. 2.

Referring to FIG. 2 and FIG. 1, the interrupter 20 contains a head casting assemblage 30, an interrupter casing assembly 31 and a bottom conductive assembly 32. The head casting assemblage is connected to the end of bushing conductor, 14, which is hollow, and which is connected to gas expansion chamber 33 through vent tubes 34 and 35 in conductive barriers 36 and 37 respectively. A conventional stationary interrupter contact 38 is also provided, which slidingly receives the upper end of elongated movable contact rod 39.

Contact rod 39 moves through interrupter casing 31 which consists of outer insulation cylinder 40 and an inner extinguishing chamber, formed of spaced insulation plates 42 fixed within insulation cylinder 43.

The bottom conductive assembly 32 then consists of a conical spring holder which is secured to tubes 40 and 43 by a conductive bottom plate 51. Contact rod 39 carries a spring plate 52 thereon which receives spring 55, which is captured between spring holder 50 and plate 52 as shown. An oil and gas seal plate 53 is then provided to form a gas-tight seal to rod 39 which still allows rod 39 to have longitudinal movement. The bottom end of rod 39 is then terminated by a disconnect contact 54.

The interrupter is then filled with oil, preferably the same oil that fills tank 10, to the oil level 60. Note that the interrupter 20 (and 21) is immersed in the oil of tank 10, but is nevertheless sealed relative to this surrounding oil. Note further that the only modifications of the conventional minimum oil interrupter necessary for use in accordance with the invention is the addition of disconnect contact 54, and the connection of vented.

bushing conductor 14 to the top of the head casting assembly 30.

When interrupters 20 and 21 are mounted within the tank 10, they are provided with conventional bottom corona shields 61 and 62 and shunt resistors, such as shunt resistor 63 in FIG. 1.

The operation of the novel combination is as follows:

When the breaker is in the closed position, shown in FIGS. 1 and 2, a current path is formed from bushing 12, through the closed contacts of interrupter 20, the closed disconnect contacts 54 and 18, crossbar l7, disconnect contact 19 and the corresponding disconnect contact of interrupter 21, the interrupter contacts of interrupter 21, and bushing 13.

To open the circuit breaker, the operating mechanism 16 is operated to cause crossbar 17 to move toward the low position shown in FIG. 1. As the crossbar 17 moves down, the compressed springs in the interrupters 20 and 21 move contact rods 39 downward to cause disengagement between interrupter contacts 39 and 38. This causes an arc to be drawn between the contacts, which arc is elongated through the interrupter plates 42. The arc causes the generation of high pressure gas from the limited volume of oil in interrupters 20 and 21, and this gas blasts axially and longitudinally through the arc and is vented through vents 34 and 35, and through bushing conductors 14 and 15. Thus, the arc is interrupted with a minimum of reaction force in the traditional manner of a minimum volume interrupter.

After arc interruption, contact rods 39 continue to move downward until they reach a stop position, shown in dotted lines in FIG. 1. The crossbar 17, however, continues to move downward to cause disconnection between its disconnect contacts 18 and 19, and the cooperating disconnect contacts 54 of contact rods 39. Thus, a disconnect gap is formed in clean oil, which is not contaminated by the discharge of arc products into the oil.

In order to reclose the breaker, the operating mechanism 16 moves crossbar l7 upwards until its disconnect contacts 18 and 19 engage disconnect contacts 54 and move contacts 39 to their closed position, and at the same time, charging springs 55.

FIG. 1 shows one possible modification of the venting scheme which could be used in accordance with the invention, wherein gas is vented into the air space above liquid level 11 of tank 10. Thus, as shown in FIG. 1, a

suitable venting tube, schematically illustrated by dotted line 80, which terminates in tube end 81 which is above the liquid level 11, permits venting of gas from tube 35 directly into tank 10. The increased pressure I within tank 10 may then be relieved by the conventional breather tube provided with tank 10. One typical breather tube is schematically illustrated in FIG. 1 as breather 82 in tank 10 and can be a simple tube which contains a metallic mesh, with the tube being angled to prevent the entrance of water or atmospheric contaminants into tank 10 while still preventing the outward flow of oil during the operation of breaker. The modified arrangement using venting line 80, which vents exhaust gases of interrupters 20 and 21 within tank 10, is advantageous in that a standard bushing structure can be used for bushings l2 and 13, since the bushings can use solid conductors instead of the hollow conductors 14 and 15 respectively.

Although there has been described a preferred embodiment of this invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. In combination, a minimum volume interrupter and a bulk oil dead tank circuit breaker housing; said minimum volume interrupter comprising a generally sealed casing having first and second interrupter contacts therein relatively movable between an open and closed position; said generally sealed casing being only partly filled with insulation oil to a given level; said bulk oil dead tank circuit breaker housing comprising: a conductive grounded housing filled with insulation oil to a given level, and first and second terminal bushings entering into said tank; said generally sealed casing being supported within said tank and being totally immersed in said insulation oil filling said tank; said first interrupter contact connected to said first terminal bushing; disconnect contact means disposed externally of said sealed casing and submerged in said insulation oil connecting said second interrupter contact to said second terminal bushing; and gas vent means for venting gas generated by said insulation oil from said sealed casing to regions exterior of said sealed casing and exterior of said tank.

2. The combination of claim 1 wherein said first terminal bushing has a channel therethrough connected to the interior of said sealed casing at one end, and to re- 5 gions external of said tank at its other end.

3. An oil circuit breaker comprising, in combination: a grounded tank at least partly filled with insulation oil, first and second terminal bushings entering said tank, 0

first and second minimum volume oil interrupters supported at the ends of said first and second terminal bushings respectively and immersed in the insulation oil filling said grounded tank, and each containing an elongated movable contact cooperable at one end thereof with a stationary contact, and each containing a sealed casing slidably penetrated by the other end of said elongated movable contact, each of said minimum volume interrupters being only partly filled with insulation oil,

a lift rod mechanismvand a conductive crossbar connected thereto; said conductive crossbar having first and second disconnect contacts thereon cooperable with said other ends of said movable contact 25 rods of said first and second interrupters, whereby lowering of said conductive crossbar causes separation of said movable and stationary contacts of said interrupters within said sealed casings and the subsequent opening of said first and second disconnect contacts in relatively clean oil within said tank,

and vent channel means extending from the interior of said sealed casings for exhausting high pressure vent gas from said sealed casings to regions external thereof and external of said tank.

4. The combination of claim 3 wherein said first and second terminal bushings contain said vent channel means for exhausting gas to regions external of said tank.

5. The combination of claim 3 which includes opening springs connected to said movable contacts for normally biasing said movable contacts to an open position relative to their respective stationary contacts.

6. The combination of claim 1 wherein said gas vent means connects the interior of said sealed casing to an air space at the top of said housing above the level of the oil filling said'housing; said air space communicating with regions external of said tank.

7. The combination of claim 3 wherein said vent channel means extends from the interior of said sealed casings into an air filled space within said tank above the level of said oil which fills said tank. 

1. In combination, a minimum volume interrupter and a bulk oil dead tank circuit breaker housing; said minimum volume interrupter comprising a generally sealed casing having first and second interrupter contacts therein relatively movable between an open and closed position; said generally sealed casing being only partly filled with insulation oil to a given level; said bulk oil dead tank circuit breaker housing comprising: a conductive grounded housing filled with insulation oil to a given level, and first and second terminal bushings entering into said tank; said generally sealed casing being supported within said tank and being totally immersed in said insulation oil filling said tank; said first interrupter contact connected to said first terminal bushing; disconnect contact means disposed externally of said sealed casing and submerged in said insulation oil connecting said second interrupter contact to said second terminal bushing; and gas vent means for venting gas generated by said insulation oil from said sealed casing to regions exterior of said sealed casing and exterior of said tank.
 2. The combination of claim 1 wherein said first terminal bushing has a channel therethrough connected to the interior of said sealed casing at one end, and to regions external of said tank at its other end.
 3. An oil circuit breaker comprising, in combination: a grounded tank at least partly filled with insulation oil, first and second terminal bushings entering said tank, first and second minimum volume oil interrupters supported at the ends of said first and second terminal bushings respectively and immersed in the insulation oil filling said grounded tank, and each containing an elongated movable contact cooperable at one end thereof with a stationary contact, and each containing a sealed casing slidably penetrated by the other end of said elongated movable contact, each of said minimum volume interrupters being only partly filled with insulation oil, a lift rod mechanism and a conductive crossbar connected thereto; said conductive crossbar having first and second disconnect contacts thereon cooperable with said other ends of said movable contact rods of said first and second interrupters, whereby lowering of said conductive crossbar causes separation of said movable and stationary contacts of said interrupters within said sealed casings and the subsequent opening of said first and second disconnect contacts in relatively clean oil within said tank, and vent channel means extending from the interior of said sealed casings for exhausting high pressure vent gas from said sealed casings to regions external thereof and external of said tank.
 4. The combination of claim 3 wherein said first and second terminal bushings contain said vent channel means for exhausting gas to regions external of said tank.
 5. The combination of claim 3 which includes opening springs connected to said movable contacts for normally biasing said movable contacts to an open position relative to their respective staTionary contacts.
 6. The combination of claim 1 wherein said gas vent means connects the interior of said sealed casing to an air space at the top of said housing above the level of the oil filling said housing; said air space communicating with regions external of said tank.
 7. The combination of claim 3 wherein said vent channel means extends from the interior of said sealed casings into an air filled space within said tank above the level of said oil which fills said tank. 